package me.gacl.web.controller;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class DownLoadServlet
 */
@WebServlet("/DownLoadServlet")
public class DownLoadServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DownLoadServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		//得到要下载的文件名
		String fileName = request.getParameter("filename");  //23239283-92489-阿凡达.avi
		fileName = new String(fileName.getBytes("UTF-8"),"UTF-8");
		System.out.println("DownLoadServlet:"+fileName);
		//上传的文件都是保存在/WEB-INF/upload目录下的子目录当中
		String fileSaveRootPath=this.getServletContext().getRealPath("/WEB-INF/upload");
		System.out.println("DownLoadServlet:"+fileSaveRootPath);
		 //通过文件名找出文件的所在目录
		String path = findFileSavePathByFileName(fileName,fileSaveRootPath);
		//得到要下载的文件
		File file = new File(path + "/" + fileName);
		//如果文件不存在
		 //如果文件不存在
        if(!file.exists()){
            request.setAttribute("message", "您要下载的资源已被删除！！");
            request.getRequestDispatcher("/message.jsp").forward(request, response);
            return;
        }
		 //处理文件名
        String realname = fileName.substring(fileName.indexOf("_")+1);
		 //设置响应头，控制浏览器下载该文件
        response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));
		//读取要下载的文件，保存到文件输入流
        FileInputStream in = new FileInputStream(path + "/" + fileName);
		 //创建输出流
        OutputStream out = response.getOutputStream();
		//创建缓冲区
        byte buffer[] = new byte[1024];
        int len = 0;
		//循环将输入流中的内容读取到缓冲区当中
        while((len=in.read(buffer))>0){
            //输出缓冲区的内容到浏览器，实现文件下载
            out.write(buffer, 0, len);
        }
        //关闭文件输入流
        in.close();
        //关闭输出流
        out.close();
	}
	
	/**
	    * @Method: findFileSavePathByFileName
	    * @Description: 通过文件名和存储上传文件根目录找出要下载的文件的所在路径
	    * @Anthor:孤傲苍狼
	    * @param filename 要下载的文件名
	    * @param saveRootPath 上传文件保存的根目录，也就是/WEB-INF/upload目录
	    * @return 要下载的文件的存储目录
	    */ 
	    public String findFileSavePathByFileName(String filename,String saveRootPath){
	        int hashcode = filename.hashCode();//hashCode是jdk根据对象的地址或者字符串或者数字算出来的int类型的数值
	        int dir1 = hashcode&0xf;  //0--15
	        int dir2 = (hashcode&0xf0)>>4;  //0-15
	        String dir = saveRootPath + "/" + dir1 + "/" + dir2;  //upload\2\3  upload\3\5
	        File file = new File(dir);
	        if(!file.exists()){
	            //创建目录
	            file.mkdirs();
	        }
	        return dir;
	    }

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}
